题目描述：

LeetCode 723. Candy Crush

This question is about implementing a basic elimination algorithm for Candy Crush.

Given a 2D integer array board representing the grid of candy, different positive integers board[i][j] represent different types of candies. A value of board[i][j] = 0 represents that the cell at position (i, j) is empty. The given board represents the state of the game following the player's move. Now, you need to restore the board to a stable state by crushing candies according to the following rules:

1. If three or more candies of the same type are adjacent vertically or horizontally, "crush" them all at the same time - these positions become empty.
2. After crushing all candies simultaneously, if an empty space on the board has candies on top of itself, then these candies will drop until they hit a candy or bottom at the same time. (No new candies will drop outside the top boundary.)
3. After the above steps, there may exist more candies that can be crushed. If so, you need to repeat the above steps.
4. If there does not exist more candies that can be crushed (ie. the board is stable), then return the current board.

You need to perform the above rules until the board becomes stable, then return the current board.

Example 1:

Input:
board = 
[[110,5,112,113,114],[210,211,5,213,214],[310,311,3,313,314],[410,411,412,5,414],[5,1,512,3,3],[610,4,1,613,614],[710,1,2,713,714],[810,1,2,1,1],[1,2,1,2,2],[4,1,4,4,1014]]
Output:
[[0,0,0,0,0],[0,0,0,0,0],[0,0,0,0,0],[110,0,0,0,114],[210,0,0,0,214],[310,0,0,113,314],[410,0,0,213,414],[610,211,112,313,614],[710,311,412,613,714],[810,411,512,713,1014]]
Explanation: 

Note:

1. The length of board will be in the range [3, 50].
2. The length of board[i] will be in the range [3, 50].
3. Each board[i][j] will initially start as an integer in the range [1, 2000].

题目大意：

模拟实现游戏“糖果粉碎传奇”

给定二维数组board，每行、列中3个或以上连续相同的数字都可以被消去（变为0表示空位），消去后位于上方的数字会填充空位。

重复直到没有更多的数字可以被消去。

解题思路：

模拟题

循环，把拟被消去的数字替换为其相反数，遍历每一列，自底向上遍历每一行，将负数消去。

当某一次消去未找到任何数字时，循环终止。

Python代码：

class Solution(object):
    def candyCrush(self, board):
        """
        :type board: List[List[int]]
        :rtype: List[List[int]]
        """
        w, h = len(board), len(board[0])
        stop = False
        while not stop:
            stop = True
            for x in range(w):
                y = z = 0
                while y < h:
                    z = y + 1
                    while z < h and board[x][z] and abs(board[x][z]) == abs(board[x][y]):
                        z += 1
                    if z - y > 2:
                        stop = False
                        while y < z:
                            board[x][y] = -abs(board[x][y])
                            y += 1
                    y = z
            for y in range(h):
                x = z= 0
                while x < w:
                    z = x + 1
                    while z < w and board[z][y] and abs(board[z][y]) == abs(board[x][y]):
                        z += 1
                    if z - x > 2:
                        stop = False
                        while x < z:
                            board[x][y] = -abs(board[x][y])
                            x += 1
                    x = z
            for y in range(h):
                x = z = w - 1
                while z >= 0:
                    if board[z][y] > 0:
                        board[x][y] = board[z][y]
                        x -= 1
                    z -= 1
                while x >= 0:
                    board[x][y] = 0
                    x -= 1
        return board

 

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